In accordance with the principles of the present invention, radiation pyrometry techniques are utilized in order to obtain accurate remote measurements of the surface temperature of hot opaque targets which diffusely reflect incident radiation, as for example, measurement of surface temperatures of metal sheets and billets in a rolling mill.
The significance of accurate temperature measurements of this type can be readily understood in view of the improvement in product uniformity obtainable. Steel billets are heated before entering the mill line. These billets must be heated to a well determined temperature in order to maintain uniformity of product. If the billet temperature varies from the desired value, the heating process can be adjusted accordingly. Conventional remote temperature measuring devices are known to be inaccurate because of uncertainty about the emissivity of the targets.
The present invention enables operators to determine the billet temperature accurately which makes it possible to regulate the billet heating with equal accuracy and thereby improve product uniformity.